A plenoptic camera is able to measure the amount of light traveling along each bundle of rays that intersects a sensor, by arranging a microlens array between a main lens and the sensor. The light field can be post-processed to reconstruct images of a scene from different viewpoints. The light field image can be used to generate a focal stack which comprises images having different depth. As a result, a user can change a focal point of the images. Compared to a conventional camera, the plenoptic camera can obtain additional optical information components for achieving the reconstruction of the images of the scene from the different viewpoints and depth by post-processing.
In a plenoptic type 1 such as the Lytro light field camera available from Lytro, Inc., an array of microlenses is placed in front of the sensor. All the microlenses of the microlens array have the same focal length and the microlens array is placed one focal length away from the sensor. This configuration enables to obtain maximum angular resolution and low spatial resolution.
Dataset of the light field image or video (e.g. acquired by a plenoptic camera, a camera array or simulated with Computer Generated Imagery (CGI)) is reorganized to form a light data volume in the vicinity of the focal plane of a front lens similar to the light field generated by a lens in the vicinity of its focal plane. Such a focal stack is schematically illustrated in FIG. 1.
A conventional focusing with a camera is simulated by selecting one of the images within the focal stack, which corresponds to moving the focalization plane perpendicularly to the main optical axis of the camera. On the contrary, a light field camera offers the ability to explore pictures from different perspectives and different focal points. Thus, a user of the light field camera can control the focus in unusual way, for example, an intersection plane across the focal stack can be defined to extract a slice image within the focal stack as shown in FIG. 1. Such slice image may provide an “all-in-focus” image along with the intersection plane.
J. P. Luke et al., “Near Real-Time Estimation of Super-Resolved Depth and All-in-Focus Images from a Plenoptic Camera Using Graphics Processing Units”, International Journal of Digital Multimedia Broadcasting Volume 2010, mentions that the focal stack can be generated using the light field image and proposes to produce the all-in-focus image from a plenoptic camera.
However, in a case where an object is located on a focal plane in the focal stack, if the intersection plane comes across the object as shown in FIG. 2, the front surface of the left end of the object will be behind the intersection plane by the distance d1 and the front surface of the right end of the object will be ahead of the intersection plane by the distance d2. Due to these distances between the object on the focal plane and the intersection plane, both ends of the object will be blurred in the image focused on the slice image after the refocusing process for the slice image is made.